A new acceptor unit containing dimethyl-2H-benzimidazole was synthesized and utilized for the synthesis of a conjugated polymer containing electron donor–acceptor pairs for OPV devices. The dimethyl-2H-benzimidazole unit was designed to act as a substitute for the BT unit of PCDTBT. This novel dimethyl-2H-benzimidazole unit has two methyl groups which can supply higher solubility than those of the BT series. A thin film of PCDTMBI, containing the dimethyl-2H-benzimidazole unit, shows two broad absorption bands with maxima at 400 and 636 nm and an absorption onset of 756 nm, corresponding to a band gap of 1.64 eV. The oxidation onset of PCDTMBI was estimated to be 0.67 V, which corresponds to a HOMO energy level of −5.47 eV. The LUMO energy level of the polymer was thus determined to be −3.82 eV. A device with a PCDTMBI:PC71BM blend had a VOC value of 0.65 V, a JSC value of 10.0 mA cm−2, and a FF of 0.48, leading to an efficiency of 3.12%. The enhanced efficiency of PCDTMBI was caused by the higher IPCE value between 400 and 700 nm and high mobility (2.2 × 10−3 cm2 V−1 s−1).
我们合成了一种含有二甲基-
2H-苯并咪唑的新受体单元,并利用这种单元合成了一种含有电子供体-受体对的共轭聚合物,用于制造 OPV 器件。二甲基-
2H-苯并咪唑单元可替代 PCDTBT 的 BT 单元。这种新型二甲基-
2H-苯并咪唑单元具有两个甲基,与 BT 系列相比具有更高的溶解度。含有二甲基-
2H-苯并咪唑单元的 PCD
TMBI 薄膜显示出两条宽吸收带,最大波长分别为 400 纳米和 636 纳米,吸收起始波长为 756 纳米,相当于 1.64 eV 的带隙。PCD
TMBI 的氧化起始电压估计为 0.67 V,对应的 HOMO 能级为 -5.47 eV。因此,聚合物的 LUMO 能级被确定为 -3.82 eV。PCD
TMBI:PC71BM 混合器件的 VOC 值为 0.65 V,JSC 值为 10.0 mA cm-2,FF 值为 0.48,效率为 3.12%。PCD
TMBI 的效率之所以提高,是因为其在 400 纳米到 700 纳米之间的 IPCE 值更高,而且迁移率也很高(2.2 × 10-3 cm2 V-1 s-1)。